I'm having too much fun being completely floored just watching a walkthrough of the game!
The possibilities seem endless. There's one scene where, in the village outside of the Vault, there is a bomb that could blow up any minute and kill all of the villagers, but no one does anything about it. So, the Sheriff asks you to help fix it, so it doesn't go off. In the video I watched, he agrees to it. Then, there is a shady guy in the bar who asks you to make it go off- he offers a reward for it, and in the video I watched, he agrees to, and gets a device that'll make the bomb go off. Then he goes back to the sheriff and chooses to tattle-tells on the guy. The sheriff gets mad and goes to the bar to talk to the guy. He tells him he is going to arrest him, but turns his back for a minute, and the guy shoots and kills the sheriff. (Then you can shoot him, of course). What's amazing is that this scene only happens if you follow several decisions, and you can end up blowing up the village or simply disarming the bomb, depending on what you choose to do and say.
Also looked at the beginning of Uncharted 2:
http://www.youtube.com/watch?v=s7BAelqlxwIwith an incredible train escape scene!

(hard to believe this is by the same people who made Crash Bandicoot and Jak & Daxter)